ABSTRACT The concept of One Health emphasizes the connection between human health, the health of animals and the health of the environment ? with the goal of improving all health. The One Health approach supports collaborations between physicians, veterinarians, dentists, nurses, ecologists, and other science, health and environmentally-related disciplines. The One Health approach is increasingly important as our population rises, agriculture intensifies, and habitat destruction increases. The goal of our ?One Health? project is to increase adolescents' understanding of One Health concepts and the importance of One Health collaborations. We will accomplish this by developing and disseminating: (1) Classroom lessons for high school students that are case-based, incorporate hands-on activities, and align with the Next Generation Science Standards, and; (2) Activities for middle and high school students that are suitable for use in a variety of informal (non-school) education settings. During this five-year project we will: ? Collaborate with scientists and life science teachers to develop case-based, hands-on One Health lessons for high school students. ? Develop and use a reliable and valid pre/post assessment to determine the impact of the One Health lessons on student learning. ? Implement a dissemination plan in which we will recruit, train and support a national network of ?teacher- presenters? to lead professional development workshops for their peers throughout the US. ? Develop activities that will be used for middle school and high school One Health field trip programs at the University of Rochester's Life Sciences Learning Center. ? Collaborate with informal educators to create One Health activities to be used in their outreach programs. This project is significant because it will improve students' understanding of the One Health approach to promoting the health of people, animals, and the environment. This project will also significantly impact teachers' awareness of One Health, and how One Health concepts are aligned with NGSS and can be incorporated into their existing curriculums. This project is innovative because it will develop One Health lessons and activities for use in a variety of settings, through partnerships with scientists, science teachers, and informal science educators. This project will also feature an innovative model for disseminating the One Health lessons to teachers nationwide using peer-to-peer professional development.